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Translation of abstract (English)

Although volumetrically small, garnet peridotite bodies are frequently formed in the internal parts of collisional belts. These ultramafic rocks provide valuable information about the interaction between mantle and crustal materials during continental collision. In particular, the trace element budgets of these rocks and the partitioning of these elements between the rock-forming minerals provide important information on metasomatic processes and the pressure-temperature-time (P-T-t) paths. In a detailed study, the inter- and intragrain partitioning of major and trace elements in the garnet peridotites from Alpe Arami (AA) and Cima di Gagnone (CdG), Central Alps (Switzerland) and from Kalskaret, Western Gneiss Region (SW Norway) were characterized using electron and ion microprobe techniques. The P-T evolution of the AA peridotite body has been the subject of ongoing controversy. Using the compositions of homogeneus porphyroclast cores, peak metamorphic conditions of about 1180 °C / 5.9 GPa were estimated based on several major and trace element thermobarometers. Li measurements revealed that the AA peridotite was continuously affected by a metasomatic overprint during exhumation as documented by the inward diffusion of Li into garnet and clinopyroxene. Compared to the CdG peridotite, the AA peridotite is characterized by significantly different trace element concentrations and d18O values in the porphyroclasts suggesting to different origins and evolutions of the two peridotite bodies. The Kalskaret garnet olivine websterite in the Western Gneiss region is characterized by well equilibrated minerals (in local subsystems) with respect to both major and trace elements. Peak metamorphic conditions were estimated at around 850 °C / 3.5 GPa. Li measurements have shown that the Kalskaret garnet olivine websterite is also enriched in Li, but compared to the AA peridotite Li diffuses out of the enriched minerals.